1. Technical Field
The present invention relates to a projector.
2. Related Art
A projector can form an image by modulating light emitted from an illumination optical system with, for example, a liquid crystal panel and enlarge and project the formed image with a projection optical system. As one of projectors, a three-plate-type liquid crystal projector having a liquid crystal panel for each of RGB colors is known.
In the liquid crystal projector, the size of the liquid crystal panel is small compared to the screen size, and the quantity of light entering a liquid crystal layer is high per unit area compared to a direct viewing-type liquid crystal display device. Accordingly, in the liquid crystal projector, the temperature of the liquid crystal layer tends to become high compared to the direct viewing-type liquid crystal display device, and the transition temperature of the liquid crystal layer to an isotropic phase is set to be high from the viewpoint of, for example, ensuring heat resistance. The compound used in the liquid crystal layer has a tendency that the transition temperature to an isotropic phase increases with the length of the π-electron conjugated system, and the transition temperature of the liquid crystal layer to an isotropic phase can be set to high by increasing the ratio of the compound having a long π-electron conjugated system in the liquid crystal layer.
However, the absorption wavelength of the compound used in the liquid crystal layer tends to shift from the ultraviolet region toward the longer wavelength side with an increase in length of the π-electron conjugated system. Consequently, the increase in ratio of the compound having a long π-electron conjugated system tends to cause decomposition of the liquid crystal layer due to light absorption, in particular, decomposition of the liquid crystal layer of the liquid crystal panel for modulating blue light. The progress of decomposition of the liquid crystal layer impairs display characteristics through reductions in contrast ratio, lightness, etc.
From the viewpoint of inhibiting the liquid crystal layer of the blue liquid crystal panel from being decomposed by light absorption, methods of cooling the blue liquid crystal panel to a temperature lower than those of other color liquid crystal panels are proposed in JP-A-10-39414, JP-A-2005-227485, and JP-A-2008-257174. According to these methods, the chemical reaction decomposing the liquid crystal layer can be inhibited from progressing, and the life of the blue liquid crystal panel can be prevented from becoming shorter than those of the other color liquid crystal panels. In addition, JP-A-2004-139018 discloses a method of controlling the temperature of a liquid crystal layer from the viewpoint of improving responsiveness of the liquid crystal layer.